Stuvia customers have reviewed more than , summaries. This how you know that you are buying the best documents. You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
|Country:||Moldova, Republic of|
|Published (Last):||12 July 2011|
|PDF File Size:||8.2 Mb|
|ePub File Size:||2.58 Mb|
|Price:||Free* [*Free Regsitration Required]|
Rodrigo J. E-mail: enemir pucminas. Examination of the testes revealed that they were paired, elongated and not fringed organs. Histologically, the testes presented three distinct regions: cranial espermatogenic; transistion espermatogenic and secretory; and caudal exclusively secretory.
Standard histochemical techniques detected neutral glycoproteins from the secretion of the tubules of the caudal region. Espermatogenesis occurred in cysts throughout the whole extension of the wall of the seminiferous tubules, which anastomosis themselves and liberated the spermatozoa into the lumen of the espermatic ducts.
The ovaries were paired, saculiformes and, histologically, they presented ovigerous lamellae that contained the cells of ovogenic ancestry. The oocytes were classified into four stages, based on their cytological characteristics and the cell layers that surrounded them.
Post-ovulatory follicles and vitelogenic oocytes in the follicular atresia process also were observed. Key words: Espermatogenesis, Loricariidae, ovogenesis, testes secretion. Gonadal organization and gametogenesis in Neotropical teleosts have been extensively studied. Some Siluriformes fishes from families Pimelodidae, Loricariidae and Callichthyidae present secretory activity in the caudal portion of the testes, sometimes forming a seminal vesicle LOIR et al.
In terms of spermatogonia distribution, the structure of teleosts testes has two types: in the most common, spermatogonia occur all along the seminiferous tubules, while in Atherinomorph fishes they are confined to the distal portion of these structures GRIER Fishes ovaries can be classified as gymnovaries, a primitive condition founded in lungfishes, sturgeons and bowfins or cystovaries, the condition that characterizes most of the teleosts, where the ovary lumen has continuity with the oviduct HELFMAN et al.
Postovulatory follicles are structures formed after oocyte release; they do not have endocrine function, present a wide irregular lumen, and are rapidly reabsorbed in a process involving the apoptosis of follicular cells DRUMMOND et al.
A degenerative process called follicular atresia reabsorbs vitellogenic oocytes not spawned. The mouth is located ventrally, with lips covered in filaments, and it feeds from detritus and algae attached to substrates. Since there are no studies focusing on reproductive characteristics in L.
Anatomy and light microscopy. The specimens were dissected and fragments from the cranial and caudal portions of the gonads of all specimens were fixed in Bouin's solution for hours. The oocytes in L. The testes of L. Both testes had spermatic ducts, which join together caudally forming a common spermatic duct that extended to the urogenital papillae.
The testes were surrounded by a tunica albuginea of connective tissue, and they had tubular and interstitial compartments. Cysts were oval-shaped, delimited by Sertoli cells insert in Fig. In resting males, the wall of the tubules in the caudal region of the testes has cubic secretory cells with no secretion in the lumen.
During spermatozoa release, cysts broke apart releasing the spermatozoa in the tubules lumen Fig. The secretion of the testes caudal region reacted positively to the PAS and ninhydrin-Shiff techniques, thereby indicating the presence of neutral glycoproteins.
Based on histological characteristics, the following spermatogenic lineage cells were identified:. Primary spermatogonia: the largest of the lineage, occurring only one per cyst, it had abundant cytoplasm, spherical central nucleus with vesicles, and a prominent nucleolus. Secondary spermatogonia: they formed cysts with two to four cells, having little cytoplasmic material, and a spherical central nucleus with a prominent nucleolus. Primary spermatocyte: originated from the last generation of secondary spermatogonias after successive mitotic divisions; they had little cytoplasmic content and slightly condensed granulated chromatin in a central nucleus.
Secondary spermatocyte: originated from the first meiotic division of primary spermatocytes, it had little cytoplasmic content and nucleus with granulated chromatin. Spermatid: originated from the second meiotic division of secondary spermatocytes, it had little cytoplasmic content and a dense spherical nucleus with a differentiated flagellum. Spermatozoa: the smallest of the lineage, they had little cytoplasmic content, with no acrosome and a nucleus with heavily condensed chromatin. Ovaries were saculiform-paired organs Fig.
Histological examination of the ovaries showed that they were also coated with the tunica albuginea of conjuntive tissue, which sent septum to the ovaric lumen forming the ovigerous lamellae that contained the oogenic lineage cells.
Based on histological characteristics, the following developmental stages of the oogenic lineage cells were identified Figs 13 to 16 :. Oogonia: the smallest of the lineage, they were rounded cells found in a nested arrangement; they had little cytoplasmic content, with vesiculous and central nucleus with a unique prominent central nucleolus and the chromatin irregularly located near the nuclear membrane.
Oogonias proliferated and produced the oocytes. Early perinucleolar oocyte: it had a bigger and strongly basophilic cytoplasm with vitreous appearance, a central nucleus and spherical peripheral nucleoli. Advanced perinucleolar oocyte: it had basophilic granular ooplasm, central nucleus and spherical nucleoli attached to the nuclear membrane.
In the ooplasm of some oocytes it was possible to identify the yolk nucleus, which in the beginning was next to the nucleus and later was displaced to the periphery. The zona pellucida was a thin layer and a unique layer of follicular cells that were pavimentous. Previtellogenic oocyte: it had cortical vesicles scattered in the ooplasm, which were slightly coloured by haematoxylin-eosin.
The nucleus was central and presented digitiform expansions and a perinuclear halo. The zona pellucida was acellular, acidophilic, and had two layers.
Follicular cells were cubic and the theca was thin. Vitellogenic oocyte: was the largest of the lineage, characterized by the presence of acidophilus yolk globules in the ooplasm. Cortical vesicles were organized in the ooplasm periphery, forming continuous cortical alveoli. The zona pellucida remained with two layers, follicular cells were prismatic, and the theca was similar in thickness to the previous stage and presents capillary blood vessels.
Postovulatory and atretic follicles. After ovulation, postovulatory follicles were identified; they presented wide irregular lumen and a wall consisting of a unique layer of follicular prismatic cells and the conjunctive theca Fig. Follicular atresia was observed in vitellogenic oocytes, which presented, through the liquefaction of yolk globules, fragmentation of the zona pellucida and integrity loss of the follicular cells Fig.
In terms of histological appearance, the cranial portion of the testis of L. The presence of spermatogonia along the whole extension of the seminiferous tubules characterizes the testis of L. In this same portion of the testis, the spermatogenic cells were organized in cysts in the walls of the seminiferous tubules, in a manner that all cells in each cyst were in the same developmental stage PUDNEY However, LOIR et al.
These substances may have similar functions as those exhibited by substances produced in the seminal vesicles of other teleosts species: acting on female attraction, in the augmentation of the seminal volume and in the fertilization process VAN DEN HURK et al.
Spermatogenesis in teleosts has two different stages: 1 the renewal and proliferation of spermatogonias by mitosis, and 2 meiosis followed by spermiogenesis SCHULZ et al. Macroscopic and microscopic appearance of the ovaries of L.
In contrast, in some salmon and trout species, the oviduct was lost secondarily, with the oocytes being released to the coelomic cavity and then, to the external environment HELFMAN et al. Advanced perinuclear oocytes in L. The two oocytary stages, early and advanced perinucleolar, of L. This two stages, previtellogenic and vitellogenic oocytes, of L. The formation of an acellular layer, the zona pellucida, during the oogenesis, is described for several teleosts species GURAYA , and it has multiple functions: it allows the passage of substances to the oocyte interior; protects it from mechanical wear and pathogens; maintains the integrity of the membrane; and promotes the adhesion of the egg to the substrate AGOSTINHO et al.
Follicular cells in L. In fact, the late perinucleolar oocytes in L. Postovulatory follicles in L. In the present study, follicular atresia was observed only in vitellogenic oocytes, in ovaries that presented histological characteristics typical of the post-spawned. As already demonstrated in the present study, the structural organization of L. The spermatogenesis can be classified as cystic, and it occurs along the whole extension of the seminiferous tubules.
The ovaries are of the cystovarian type and the oogenesis was characterized histologically by four developmental stages. Revista Brasileira de Biologia , Rio de Janeiro, 42 1 : Revista Brasileira de Biologia , Rio de Janeiro, 47 3 : Continuous gametogenesis in the neotropical freshwater teleost, Bryconops affinis Pisces: Characidae.
A comparative cytological and cytochemical study of the oogenesis in ten brazilian teleost fish species. European Archives of Biology , Liege, : Comparative morphology of the yolk nucleus Balbiani body in freshwater neotropical teleost fish. Revista Brasileira de Biologia , Rio de Janeiro, 55 2 : Belo Horizonte, 5 5 : Spermatogenesis and spermatology of some teleost fish species.
Reproduction Nutrition Development , Paris, 26 : Guia ilustrado de peixes da bacia do rio Grande , p. VAZ; V. REIS; R. VARI; Z. Phylogeny and Classification of Neotropical Fishes. Post-ovulatory follicle: a model for experimental studies of programmed cell death or apoptosis in teleosts. Subfamily Loricariinae, p. REIS; S. Check list of the freshwater fishes of South and Central America.
Cellular organization of the testes and spermatogenesis in fishes. American Zoologist , Thousand Oaks, 21 : Ovarian germinal epithelium and folliculogenesis in the common snook, Centropomus undecimalis Teleostei: Centropomidae. Journal of Morphology , New York, : Testicular structure of three species of neotropical freshwater pimelodids Pisces, Pimelodidae.
Revista Brasileira de Zoologia , Curitiba, 21 2 : The cell and molecular biology of fish oogenesis.
Apuntes ovogénesis y espermatogénesis
Biodiversity Heritage Library
Histological description of oogenesis and spermatogenesis in the cultured shrimp, Litopenaeus vannamei. Both processes were studied in cultured organisms under reproduction conditions in the laboratory. Spermatogenesis was characterized at light microscopy from spermatogonia and their gradual maturation into primary and secondary spermatocytes, early, mid and advanced spermatids and sperm. The process is synchronous in regions of seminiferous tubules, and asynchronous in neighboring tubules, generating cells at different stages up to mid spermatids in the testicles. Advanced spermatids and spermatozoa were only observed in the vasa deferentia; this finding appears not to be universal in Penaeidae. A pesar de la importancia comercial de L.
Los procesos meioticos
Rodrigo J. E-mail: enemir pucminas. Examination of the testes revealed that they were paired, elongated and not fringed organs. Histologically, the testes presented three distinct regions: cranial espermatogenic; transistion espermatogenic and secretory; and caudal exclusively secretory. Standard histochemical techniques detected neutral glycoproteins from the secretion of the tubules of the caudal region.
espermatogenesis y ovogenesis......